Altis gives you the ability to swap between firms should you be a part of or working for, more than one legal firm.
When you login, you will not have been assigned to a firm, so you must search for and select your firm from the alphabetised list. This will then pull up all the transactions you have been assigned to within that firm.
To swap firms, simply head back to your dashboard, search for your other firm from the list, and select it. This will swap your firm.